This invention relates to an air conditioner having an outdoor air introducing mechanism and, more particularly, to a control system suitable for optimizing the ability to cool outdoor air in response to changes in the cooling load and/or the ventilation rate.
In a conventional system of controlling an air conditioner, an outdoor air introduction damper is driven in such a manner that, during the ON state of a cooling thermostat serving as a room temperature sensor, the temperature of an air consisting of room return air and outdoor air mixed with each other becomes equal to a set point of a mixed air thermostat the set point of which can be changed only by a manual operation and that, during the OFF state of the cooling thermostat, the opening of the outdoor air introduction damper is set to the minimum opening.
U.S. Pat. No. 4,244,193 discloses an example of a type of cooling system utilizing outdoor air. This system utilizes, in order to reduce energy consumption of the cooling system, outdoor air by employing an auxiliary unit having a simple structure and capable of being easily mounted.
This type of auxiliary unit is used in combination with a mechanical cooling system so as to assist this cooling system in cooling a room by utilizing outdoor air.
To first reduce the temperature of air in the room to an intermediate temperature, a mechanical cooling system or a combination of a mechanical cooling system and an auxiliary unit is utilized.
The room is cooled at a predetermined low temperature while an outdoor air temperature reaction fan for introducing outdoor air having a comparatively low temperature into the room when the room temperature is lower than a predetermined temperature is operated.
This type of conventional system has been designed to set the mixed air temperature by a manual change-over operation without any consideration for means to optimize the setting of the mixed air temperature in response to variations in the cooling load and the ventilation rate. It the cooling load exceeds a level assumed at the time of the initial setting of the mixed air temperature, the cooling power becomes inadequate to maintain the desired low temperature and, if the ventilation rate becomes lower than the set rate, the cooling power also becomes inadequate and the user have to reset the mixed air temperature to a lower value. Conversely, if the cooling load becomes lower than the initial setting level or if the ventilation rate becomes higher, the cooling power becomes excessively large and the cooling thermostat is switched off. At this time, however, the opening of the outdoor air introduction damper is reduced to the minimum, and air is supplied to the interior of the room at a temperature substantially equal to the room return air temperature, resulting in an increase in the variation of the supplied air temperature.